The invention relates generally to haptic feedback systems, and more particularly, to a haptic feedback system associated with an automotive throttle actuator.
Control of a vehicle through the use of electronically-controlled mechanisms rather than mechanically-controlled mechanisms has been implemented in different forms. Typically called “steer-by-wire,” “drive-by-wire,” or “control-by-wire,” electronically-controlled mechanisms direct electric motors and/or hydraulic or pneumatic control systems, to perform mechanical operations rather than a user directly performing the mechanical operations using a mechanical interface. For example, in a standard mechanical steering system in an automobile, the user moves a steering wheel, which mechanically rotates rods, gears, and other mechanical elements to turn the front wheels based on the motion of the steering wheel. In a drive-by-wire system, the user rotates the steering wheel (or moves some other type of manipulandum) to generate control signals to control one or more electric motors, hydraulic actuators, etc., which turn the front wheels. No mechanical linkage between steering wheel motion and wheel motion exists (unlike power assisted steering). A processor (microprocessor, etc.) can be used to sense motion of the steering wheel and correlate it with motor control to achieve the corresponding steering of the wheels.
Another vehicle control system that is typically now electronically-controlled rather than mechanically-controlled is the vehicle throttle control. Automotive throttle pedals historically provided a characteristic force against a driver's foot as a function of pedal displacement. In the past, this force was associated with mechanical linkages and a cable connecting the throttle pedal to the throttle valve in the engine. Rather than direct pedal control of throttle position, newer Electronic Throttle Control (ETC) systems use servo-valves.
In ETC systems, the throttle pedal provides only a sensor input to the ETC and, in the absence of the inherent friction associated with traditional mechanical throttle valve linkages, the characteristic force feedback to the driver must be recreated by other means. The force profile associated with known throttle control generally includes an increasing reaction force against the driver's foot the farther the pedal is depressed. This increased physical effort applied by the driver is consistent with the increased effort associated with the vehicle to achieve the desired acceleration.
Known mechanical systems that reproduce and/or simulate the necessary friction, however, are not ideal due to variation in the friction output associated with various parameters including system component inconsistencies, mechanical wear of system components, and variation in operating environment (e.g., temperature, humidity, atmospheric pressure, etc.).
A need exists for improvements in feedback to throttle controls using throttle-by-wire systems to produce desired haptic effects.